The subject of this patent application relates generally to wind turbines, and more particularly to a vertical-axis wind turbine apparatus having a protective screen.
Applicant(s) hereby incorporate herein by reference any and all patents and published patent applications cited or referred to in this application.
By way of background, for over a century, wind turbines have been utilized in converting wind-driven kinetic energy into electricity. In recent years, wind turbines have become an increasingly important source of renewable energy and are being used by many countries as part of a strategy to reduce reliance on fossil fuels. While most wind turbines are configured for rotating about a horizontal axis, a relatively newer type of wind turbine—known as a vertical-axis wind turbine (“VAWT”)—is configured for rotating about a vertical axis. One advantage of this arrangement is that the wind turbine does not need to be pointed into the wind to be effective, which is an advantage on a site where the wind direction is highly variable. It is also an advantage when the wind turbine is integrated into a building because it is inherently less steerable. Also, the generator and gearbox are able to be placed near the ground, using a direct drive from the rotor assembly to the ground-based gearbox, which improves accessibility for maintenance purposes.
The speed at which a wind turbine—both horizontal-axis and vertical-axis—rotates must be controlled for efficient power generation and to keep the turbine components within design speed and torque limits. All wind turbines are designed for a maximum wind speed—often referred to as the “survival speed”—above which they will suffer mechanical damage. With respect to VAWT's, electrical or mechanical brakes are often employed and used for slowing down the blade rotation as needed to prevent the turbine from exceeding its survival speed. However, such braking means require a potentially significant expenditure of energy when utilized. Additionally, depending on the speeds, the heat generated by such braking has the potential to create a fire inside the nacelle if used to stop the turbine from full speed.
Therefore, there remains a need for minimizing the energy required to brake and protect a vertical-axis wind turbine during survival speed winds. Aspects of the present invention fulfill these needs and provide further related advantages as described in the following summary.